Department of Molecular Pathology, Osaka City University Graduate School of Medicine, Osaka, Japan.
Osaka Occupational Health Service Center, Japan Industrial Safety and Health Association, Osaka, Japan.
Toxicol Sci. 2019 Jun 1;169(2):456-464. doi: 10.1093/toxsci/kfz051.
Acetoaceto-o-toluidide (AAOT) is made from ortho-toluidine (OTD) and is used for the synthesis of pigments. A report of occupational urinary bladder carcinomas in Japanese workers chronically exposed to OTD and AAOT has recently been published. OTD is a well-known human urinary bladder carcinogen; however, little is known about the toxicity and the carcinogenicity of AAOT. The aim of the present study is to evaluate the toxic effects of AAOT on urinary bladder epithelium. In vitro, the cytotoxicities of AAOT and OTD were evaluated in rat (MYP3) and human (1T1) urothelial cells. The LC50 of AAOT was higher than that of OTD in both MYP cells and 1T1 cells. In vivo, 6-week-old male and female F344 rats were fed diets supplemented with 0%, 1.5%, or 3% AAOT for 4 weeks. Incidences of simple hyperplasia, cell proliferative activity, and γ-H2AX expression, which is a novel marker for the prediction of carcinogenicity, were significantly increased in a dose-dependent manner in the bladder urothelium of male and female rats administered AAOT. Furthermore, in male and female rats administered AAOT, the major urine metabolite of AAOT was OTD. These results demonstrate that AAOT has proliferation-enhancing activity and suggest that OTD metabolized from AAOT may play a pivotal role in the deleterious effects of AAOT in rats. The results of the present study also indicate that AAOT, like other carcinogenic aromatic amines, is likely to be a human bladder carcinogen.
乙酰乙酰邻甲苯胺（AAOT）由邻甲苯胺（OTD）制成，用于合成颜料。最近发表了一份关于日本工人长期接触 OTD 和 AAOT 导致职业性膀胱癌的报告。OTD 是一种众所周知的人类膀胱癌致癌物；然而，对于 AAOT 的毒性和致癌性知之甚少。本研究旨在评估 AAOT 对膀胱上皮的毒性作用。在体外，评估了 AAOT 和 OTD 在大鼠（MYP3 和 1T1）和人（1T1）尿路上皮细胞中的细胞毒性。AAOT 的 LC50 在 MYP 细胞和 1T1 细胞中均高于 OTD。在体内，6 周龄雄性和雌性 F344 大鼠分别用添加 0%、1.5%或 3%AAOT 的饮食喂养 4 周。AAOT 给药的雄性和雌性大鼠膀胱尿路上皮中的单纯性增生、细胞增殖活性和γ-H2AX 表达（一种预测致癌性的新型标志物）的发生率呈剂量依赖性增加。此外，在雄性和雌性大鼠中，AAOT 的主要尿液代谢物是 OTD。这些结果表明 AAOT 具有促进增殖的活性，并提示由 AAOT 代谢的 OTD 可能在 AAOT 对大鼠的有害影响中发挥关键作用。本研究的结果还表明，AAOT 与其他致癌芳香胺一样，可能是人类膀胱癌的致癌物。
